1. Field of the Invention
The present invention relates to an apparatus of measuring capacitance and method thereof.
2. Related Background Art
Conventional apparatuses of measuring capacitance are provided with a power supply for applying a voltage to capacitor, a voltmeter of measuring a voltage applied to the capacitor, and an amperemeter of measuring a current flowing through the capacitors when the voltage is applied to the capacitor. The voltage from the voltmeter and the current from the amperemeter are sent to a capacitance measuring part. This capacitance measuring part measures electrical capacitance and dissipation factor.
Incidentally, the electrical capacitance measured by the capacitance measuring part largely depends on voltage value, due to dielectric materials of the capacitors. Because of this, the measuring value of the electrical capacitance rises when the voltage rises, and the measuring value of the electrical capacitance falls when the voltage falls. In such case, it is impossible to measure the electrical capacitance of the capacitors with high accuracy.
An object of the present invention is to provide an apparatus of measuring capacitance and method thereof it is possible to measure capacitance of capacitors with high accuracy.
To achieve the foregoing object, an apparatus of measuring capacitance, comprising:
a power supply for applying a voltage to a capacitor;
a voltmeter of measuring the voltage applied to the capacitor;
an amperemeter of measuring a current flowing through the capacitor when the voltage is applied to the capacitor;
a determining part for determining whether or not the voltage applied to the capacitor deflects from voltage between upper-limit and lower-limit values, and
a capacitance measuring part of measuring electrical capacitance based on signals from said voltmeter and said amperemeter.
According to the present invention, the voltage from the power supply is applied to the capacitors, and the voltage applied to the capacitor is measured by a voltmeter, as well as current flowing through the capacitor is measured by an amperemeter. A capacitance measuring part measures electrical capacitance based on the voltage from the voltmeter and the current from the amperemeter. During the measuring period, whether or not the voltage measured by the voltmeter deflects from a voltage between upper-limit and lower-limit values is determined by a determining part. When determined that the voltage applied to the capacitor does not deflect from the voltage between upper-limit and lower-limit values, the electrical capacitance of the capacitor is measured.
Thus, because the present invention measures the electrical capacitance only at a range that measuring accuracy of the electrical capacitance of the capacitor is high, it is possible to improve the measuring accuracy of the electrical capacitance of the capacitor.